Can you find out the remainder when 3^300 is divided by 5?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

Can you make the number 24 by utilizing the numbers 1, 3, 4 and 6? You must use one number only one time and you can use mathematical operation symbols anytime anywhere.

Can you find the missing number in the third row?
35 20 14
27 12 18
5 2 ?

What's a single-digit number with no value?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

Can you write down eight eights so that they add up to one thousand?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?